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November 15, 2013

Benefits of Virtualizing Citrix XenApp

Andrew Wood - Atlantis


To virtualize your Citrix XenApp servers, or not? It is still a noble question. Virtualization underpins today’s data centres as companies look to drive down costs of providing services, and to quickly and effectively respond to demand for change.

But, what are the benefits of virtualizing servers hosting Terminal Services? Granted, the majority of those servers are running Citrix XenApp, but Citrix XenApp isn’t the only product on the market. Quest vWorkspace, Ericom Powerterm WebConnect, ProPalms, Systancia, to name a few, all offer additional services like Citrix XenApp to the core Microsoft Remote Desktop Session Host (RDSH) formerly known as “Remote Desktop Services” or “Terminal Services”.  Yet, given the large market share Citrix still commands the question is more often than not, why Virtualize Citrix XenApp?

Is a Physical Citrix XenApp Host “good enough”?

When virtualizing applications and desktop, Microsoft’s RDSH service still provides the most cost effective licensing option for supporting users at scale across a variety of devices as shown in Login Consultants useful white paper on Decoding Microsoft’s VDI Licensing Arcanum.

While XenDesktop 7 introduced App Edition, this is still too new technology for many organisations.  Citrix XenApp 6.5 R2 is considered more mature and reliable and, today, has a greater number of features. RDSH servers, such as Citrix XenApp, are often cited as being ‘unvirtualizable’. They typically run with high utilization of CPU,  memory and disk resources. As RDSH server farms often support a high number of users, core server builds tend to be standardized, and application deployment to those servers automated. If you’ve already a standardized and automated environment, if you’ve already high hardware utilization: why go to the bother and cost of adding in another service? Simply moving to XenApp 6.5 on 2008R2 is often considered “good enough”. However, a extra investment can reap greater rewards. What other services can virtualized Citrix XenApp drive?

Why Virtualize Citrix XenApp Workloads?

There are a number of benefits that virtualizing Citrix XenApp environment can bring to help drive better performance for users, reduce the impact on projects and ultimately lower costs:

Hardware Abstraction  Virtualization’s goal of standardization and automation is achieved by abstracting the server operating system from the device hardware. Many Citrix XenApp server farms grow over time.  As a Citrix farm is maintained it is not unusual to have a range of server hardware in use. This leads to a problem of managing and maintaining builds for different hardware platforms, different device drivers, different patching requirements. A new server type necessitates a new server image.  With hardware abstraction, the build management process is simplified. More readily automated. The introduction of new hardware does not need major changes, and isn’t another image to be added to the image management system;  reducing operational costs for your farm and helping to minimize the risk of cost overruns during hardware refreshes.

Indeed, there are some hardware uses cases where you need virtualization today: NVIDIA for example, does not currently support their GRID cards on bare metal installations.

Availability  or redundancy is typically provided by having more than one server configured. If a server fails, users sessions are terminated – but they can re-connect on another host and carry on. Yet, they have been  disrupted. With virtualization, it is possible to move a server instance to different hardware in case of failure, or to isolate a server instance that is behaving erratically. Still, failure is not always about server hardware: applications and environments can fail. Here, having server instances with fewer users assigned allows for a smaller failure domain and potentially easier maintenance as users can be divided into smaller discrete groups reducing the impact of any individual server update: allowing a large problem to be more readily broken down into more manageable smaller parts.

Consolidation: Many farm designs require servers to be placed into “silos” for a number of reasons:

1. Allowed resource demanding applications to be isolated from the main ‘standard/desktop application delivery servers.

2. Allowed applications that may conflict when installed on the same server (e.g. different versions of Microsoft Office, or Internet Explorer) to be hosted.

3. Allowed non-standard applications to be installed and configured on servers outside of the standard build.

4. Allow better hardware resource utilization for x32 bit operating systems like Windows 2003 or Windows 2008.  While those OS environments may be unsupported by the vendor from a budget and operation standpoint there is still a requirement to maintain them.  With virtualization new servers can be used to consolidate older servers.

5. Allowed servers to be managed by different groups (e.g. third-party to manage an application, or to have development and test environments).

Silos lead to servers being under-utilized. While Citrix XenApp 6.5 offers features to reduce the requirement for siloing, and the Microsoft RDS license includes the use of App-V,  from an application compatibility perspective there are still organisations supporting applications that don’t fit well with application virtualization, and there are applications that have specific resource demands. More importantly, while there is concerted move to consolidate session host services x64 operating, there are still many organisations running services on x32 Windows 2003 and Windows 2008. There is a benefit to having specific use RDSH servers consolidated together to reduce the need for ever expanding hardware, reducing TCO.

Better performance:  Adding a hypervisor reduces capacity for a server running Terminal Services doesn’t it? Native hardware interaction is going to deliver the best performance: and you would be right. However, while the difference in performance used to be large for virtualised Terminal Services servers, this has improved.

Research from Citrix  Pedal to the Metal: Bare Metal Scaling of XenApp 6.5 Hosted Shared Desktopsand Project VRC analysis of Terminal Services workloads running on the latest generation hardware and hypervisors show that while a bare metal server still has a small edge in terms of raw density, the performance of virtualized servers was comparable as long as resources weren’t over-committed on the host. Indeed having a virtualised platform can allow additional tools to help drive additional performance by optimizing resource usage – e.g. Atlantis ILIO can optimise even local server storage helping to increase performance through optimized use of resources, if using with an NVIDIA GRID card you have more control over the number of users per GPU.

Simplified Automation and Management: to reduce expense and ease management most organisations have adopted a “virutal first” policy for new services. As the foundation to building a software defined data centre , the goal is to drive out limitations due to servers hosted on physical hardware.  Having a virtualised environment allows a faster migration (or deployment) to Citrix XenApp 6.5 and beyond helping to reduce the risk of cost overruns during migration.

Virtualizing Citrix XenApp Delivers  Real Advantages

Virtualizing your Microsoft RDSH servers will require a hypervisor deployment. Increasingly, the hypervisor deployment has little license cost value. Virtualization allows hardware abstraction bringing with it simplified image management and reduced time to deliver OS upgrades. Virtualization brings higher availability and faster recovery allowing faster return to normal operations and reducing the impact of failure on the business. Virtualization can reduce a server instance failure domain, allowing for greater flexibility with updates and again, reducing the business impact on failure. It is this range of advantages that has driven Citrix XenApp virtualization to be the norm rather than the exception.

That said, there are common issues in moving to a virtualised environment. With the fortune of benefits, there are  slings and arrows best avoided. Sizing storage and performance demand correctly is key. Using the right server hardware and the best tools can ensure that the project delivers as required. We’ll  discuss how to make the best of your virtualized Citrix XenApp environment  in Part II – Benefits of Virtualizing Citrix XenApp with Atlantis ILIO and IBM Technology.

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